Google Drive -- drive.google.com
Google Drive is 15 GB of free storage for any kind of file. Create documents, presentations, spreadsheets, forms, and pictures that may be shared and edited by a group of people in real time.
To Access Drive from other Google Apps, click the Apps icon and select Drive.
Click "Create" to start a new document, or click "Shared with Me" to access documents that others have given you access to.
To share a document that you have created so others can edit or view, first click on that document to open it. Then click "Share" in the top-right corner. The screen that pops up will allow you to invite users by email address or Google+ name, and to review who has access to the document.